The present invention is directed to overload current protection devices.
Fuses are utilized as overload protection, for example in low-voltage networks, household connections, electrical devices or in electronic circuits, and should interrupt the circuit given unacceptably high currents, for example in the case of a short. In the simplest case, these overload current protections are fashioned as cut-out fuses and are then composed of a piece of resistance wire that melts at a specific current load.
Particularly in electronic circuits that are constructed on printed circuit boards, a number of different electrical or, respectively, electronic circuits are utilized that are sensitive to high currents and that could even cause the printed circuit board to catch fire in case of overload due to the dissipated heat that arises.
It is known from the prior art to protect individual electrical components. For example, German patent document DE 25 31 438 C3, incorporated herein by reference, discloses that a tantalum solid electrolyte capacitor can be protected against short-circuit currents caused by incorrect poling by introducing a cut-out fuse between the cathode terminal and contacting.
It is also known, for example from European publication EP 0 187 921 B2, incorporated herein by reference, to provide a cut-out fuse in an electrical capacitor, this cut-out fuse being composed of a coated circuit board wherein the conductive material represents a current fuse.
In a regeneratable electrical capacitor, it is also known to divide the metal coat on the foil into a great plurality of metal areas electrically connected in parallel, each of these being respectively connected to the electrical terminals via a constriction, i.e., a narrowing in width or height, or both, of the current flow path (German Letters Patent 723 291, incorporated herein by reference). Given breakdowns at one of the individual metal areas, it thereby becomes possible that only the constriction lying in front of this area melts through due to the short-circuit current, so that this area is shut off whereas the capacitor continues to be functional.
Given all of the described measures, however, only a single electrical component is disconnected, whereas other components are unprotected. Since it is not economically feasible to provide every component with overload current protection, a traditional overload current protection device that is fashioned as a cut-out fuse is generally integrated in the input circuit given electrical or, respectively, electronic circuits arranged on printed circuit boards.
Since great numbers of these circuits are manufactured for a great variety of applications, the costs of overload current protection becomes a consideration.